Is it sort of trivial to make the adjustments in nvOC for going over 13 GPUs? I should be crossing that threshold soon enough..
The default setting in nvOC support up to 14 GPU's. With a bit of editing (1bash, 3main, auto_temp, xorg.conf) you should be able to add support for more GPU's.
Someone reported that got 19 GPU's to work with a bit of editing, but do you really want to add more GPU's to one motherboard? If something goes wrong, all 19 GPU's will go down and not mine... not to mention troubleshooting nightmares if one GPU or riser start acting up, then there is power strugle...